Apparatus for well drilling operations with explosives



Nov. 2, 1965 H. ROBINSON, JR.. ETAL 3,215,074

APPARATUS FOR WELL DRILLING OPERATIONS WITH EXPLOSIVES Filed June 13,1963 3 Sheets-Sheet 1 FIG. IB

PRIMACORD 33 FIG- IA- ll 64 s4 35- ,SHAPED CHARGE l3 -LINER l7 SHIELD/40c 43q 2 2| 2 49ut 28 3 23 3 t so t 29 IGNITER -SYNDETIC SQUIB CHARGE3| INVENTORS.

LEON H. ROBINSON,JR., ROBERT H. FRIEDMAN,

ATTORNEY.

1965 L. H. ROBINSON, JR.. ETAL 3,215,074

APPARATUS FOR WELL DRILLING OPERATIONS WITH EXPLOSIVES Filed June 15',1963 3 Sheets-Sheet 2 III.

I I l l I l I I DRILLPIPE %DRILLING FLUID 7-F'IRING HEAD DRILLING HEAD IFIG. 22. CHARGE HOUSING 6 l8 M S ECON D S INVENTORS.

LEON H.ROBINSON,JR., ROBERT H.FR|EDMAN,

IIIIIIII' II L I HMIII II.TII' HII-| |||1|| Nov. 2, 1965 L. H. ROBINSON,JR.. ETAL 3,215,074

APPARATUS FOR WELL DRILLING OPERATIONS WITH EXPLOSIVES Filed June 15,1963 3 SheetsSheet 3 FIG-4. FIG. 5. FIG.8. FI6.9.

I M SECONDS M SECONDS M SECONDS M SECONDS M SECONDS Fl 6 l0 Fl 6. l l Fl6. l2. F IG. I3. F l6. l5.

I 6 r r M SECONDS M SECONDS M SECONDS M SECONDS M SECONDS FIG. l6. Fl 6-l7- Fl 6. l8. FIG. I9. FIG. 20.

M SECONDS I3 M SECONDS l4 M sscouns M sscouos I6 M SECONDS I7 INVENTORS.u SECONDS LEON H. ROBINSON JR.

ROBERT H.FRIEDMAN,

United States Patent Fed 3,215,074 APPARATUS FOR WELL DRILLINGOPERATIONS WITH EXPLOSIVES Leon H. Robinson, Jr., and Robert H.Friedman, Houston,

Tex., assignors, by mesne assignments, to 250 Production ResearchCompany, Houston, Tex., a corporation of Delaware Filed June 13, 1%3,Ser. No. 287,544 2 Claims. (Cl. 102-20) This invention relates toexplosive charge apparatus for use in boreholes, and more particularlyto explosive charge apparatus for use in connection with well drillingoperations.

Various techniques have been developed for the purpose of using thedirectional blasting characteristics of explosive-jet shaped charges todrill boreholes in the earth. A particularly successful technique isthat described in US. Patent No. 3,070,010. In this technique use ismade of elongated shaped charges and elongated gauging charges adaptedto be pumped down a well pipe. The jet charges and gauging charges areinjected into a stream of drilling fluid pumped down a well pipeaccording to a predetermined sequence. Initially, a shaped charge ispumped down the pipe and is detonated when it reaches the bottomthereof, preferably by building up a hydrostatic pressure ofpredetermined magnitude in the borehole. A hole is blasted into theearth at the bottom of the well bore into which a gauging charge isinserted after detritus is removed therefrom by circulation of drillingfluid. The gauging charge, which may be a brisant or unbrisant explosivematerial, or a combination thereof, is detonated while tamped withdrilling fluid. Drilling fluid is circulated after each detonation of anexplosive charge so as to remove earth fragments and fragments ofexplosive charge housings from the borehole.

Manifestly, it is desirable to blast as deeply into the earth aspossible with each shaped charge so as to extend the borehole as fardown as possible after each sequence of shaped charge and gauging chargeor charges.

In accordance with one aspect of the present invention, there isprovided an elongated housing terminating in an ogive at one endthereof. Supported in the housing are a plurality of explosive-jetshaped charges, the charge supported in the end of the housing oppositethe ogive having a conical opening facing toward the ogive, with theaxis of the conical opening being directed substantially at the point ofthe ogive. The additional shaped charges are supported between the firstshaped charge and the ogive. Each of the additional charges has anopening therethrough at least a portion of which is frusto-conical inshape, the axis of the frusto-conical portion being substantiallycolinear with the axis of the conical opening of the first shapedcharge. Connecting each adjacent pair of said shaped charges is asyndetic explosive charge having a burning time at least equal to thetime required for substantially the entirety of the explosive-jetproduced by the shaped charge farthest removed from the ogive to passinto the opening through the other of said each adjacent pair of shapedcharges. The cone angle of the conical and frusto-conical openings ofthe shaped charges are substantially equal. Differential pressureresponsive firing means are provided for igniting the first shapedcharge responsive to hydro-static pressure of a given magnitude.

Objects and features of the invention not apparent from the abovedescription will become evident upon consideration of the followingdetailed description of the invention taken in connection with theacwmpanying drawings, wherein:

3,Z15,74 Patented Nov. 2, 1965 FIGS. 1A and 1B, taken together, are across-sectional view of an embodiment of the invention;

FIG. 2 is a cross-sectional view of the apparatus of FIG. 1A taken alongsection 22;

FIG. 3 is a cross-sectional view of the apparatus of FIG. 1A taken alongsection 33;

FIGS. 422 are simplified views of a pair of the shaped explosive-jetcharges shown in FIG. 1B, illustrating the manner in which theexplosive-jet produced thereby is formed; and

FIG. 23 is a cross-sectional view of a portion of a borehole beingdrilled by the apparatus of the present invention.

With reference now to FIGS. 1A, 1B, 2, and 3, there is shown anelongated housing comprising housing sections 1, 3, and 5. The lower endof housing section 5 terminates in an ogive 51, which preferably is ofrelatively thin material. Supported within the housing are a pluralityof shaped explosive-jet charges 37, 49a, 49b, and 4%. Shaped charge 37has a conical opening facing toward ogive 51. The axis of the conicalopening is directed substantially at the point of the ogive 51. Shapedcharge 37 is provided with the usual liner 39, which may be formed ofcopper or aluminum. The explosive jets 49a, 49b, and 490 have openingstherethrough, at least a portion of which is frusto-conical in shape.The axes of the frusto-conical openings of shaped charges 49a, 49b, and490 are substantially co-linear with the axis of the conical opening ofshaped charge 37. Interconnecting shaped charges 37 and 49a is asyndetic or connecting charge 40a, which may be formed of an explosivematerial such as composition B, which is a combination of RDX and TNTdescribed in the text The Science of High Explosives by M. A. Cook(Reinhold Publishing Co., 1958). The syndetic charge 40a is held inposition by a metal shield 45a comprising an upper frusto-conicalsection 43a, a lower frusto-conical section 47a (which also could formthe liner for shaped charge 4%) with an annular connecting section. Thesyndetic charge 40a is generally annular in shape and has a burning timefrom the lower end of the upper shaped charge 37 to the upper end oflower shaped charge 4% such that the explosive-jet produced by the uppershaped charge will have passed into the opening of the lower shapedcharge by the time that the lower shaped charge is ignited by thesyndetic charge. This burning time may be determined by the conicalangle of the metal shield section 43a and by the shortest distance fromthe lower end of line 39 to the upper end of shaped charge 49a measuredalong the syndetic charge. More particularly, this distance (D) may bedetermined from the formula where V is the detonation velocity of thesyndetic charge, and

V is the velocity of the jet, and

X is the perpendicular distance from the lower end of the shaped chargedetonating the syndetic charge to the upper end of the next shapedcharge. The distances D and X are shown in FIG. 1B.

The lower shaped charges 4% and 49c are positioned in the housingsection 5 in a manner similar to that of shaped charge 4%. The lengthsof syndetic charges 4% and 400 are determined in the same manner asdescribed above for syndetic charge 40a. Shaped charges 4% and 490 areprovided with metal shields 45b and 45c which are similar in design tometal shield 45a. The axes of the frusto-conical openings of charges 4%,4% also lie on the conical axis of the opening of explosive charge 37.

It should be noted that the explosive charge 37 is held in position by asubstantially conical holding member 35, to which is connected a lengthof Primacord 33 for igniting the upper shaped charge 37. The Primacordis brought sufficiently close to shaped charge 49a to ignite the shapedcharge at the upper end thereof. The Primacord 33 is fired by theapparatus illustrated in FIGS. 1A, 2, and 3. An igniter squib at theupper end of Primacord 33 is positioned in a fitting 2 supported withinhousing section 3. The upper housing section 1 supports a piston housing7, within which is positioned a plunger or piston 11. The piston housingthreads into an elongated spring housing 17. At the lower end of thespring housing is an annular section 28 projecting upwardly into thespring housing for supporting a shear pin 27 and a firing pin 23. Thefiring pin 23 is positioned immediately above the igniter squib 31. Acompression spring 19 is held between a plate 15 connected to plunger 11by connecting rod 13, and a plate 21 afiixed to the upper end of firingpin 23. Responsive to pressure exerted upon the upper face of plunger11, the plunger 11 moves downwardly as a result of the differentialpressure between the upper end of housing section 1 and port 54. Thepressure exerted on the firing pin 23 by spring 19 will increase untilpin 27 shears, releasing the firing pin 23 to detonate the igniter squib31.

Holes 60 and 62 and port 64 are provided to place the underside of thepiston at the pressure around housing section at the level of port 64.Thus, the differential pressure across the piston will be the differencebetween the pressure at the upper end of the capsule and the pressure atport 64. The conical holding member 35 may be sealed fluid-tight at itsedges to the housing section 5 so that liquid cannot penetrate belowmember 35. As shown, the member 35 is formed as port of housing section5.

When the lower housing section 5 is made heavy to withstand thehydrostatic pressure between the interior and exterior of the housing,then some provision should be made to assure it disintegrates when thecharges are fired. This can be accomplished by making that section froma brittle material such as cast iron or a brittle alloy steel.Additional safety can be obtained by serrating the housing in the mannerof a grenade. To couple the force of the explosion of the shaped chargesto be more certain the housing is shattered, an acoustic coupling may beused within the housing, as by filling the spaces between the chargesegments and the housing with a granular material as the charge islowered into the housing. This can be done by filling the space with aninert powder or with a paste of a granular material as the chargesections are lowered into the housing. It is essential that thisacoustic coupling material does not make a physical bond with thehousing, and accordingly, such materials as fine sand, clay, or baritesshould be used rather than a cementitious material which might hydrateand bond. An alternate material to fill this space could be a slowburning explosive material such as black powder or amatcl (a mixture ofTNT and ammonium nitrate). This explosive may be packed as a powder ormolded in shape and inserted as the shaped charge is placed in thehousing.

Referring now to FIG. 23, there is shown a drill pipe 55 having adrilling head 57 at the lower end thereof. The drilling head 57 is forthe purpose of reaming out hole in the event such is desirable. A shapedjet housing constructed in accordance with the invention is shown ashaving been landed in the borehole at the bottom end thereof. As theshaped charge housing passes through the bore of the drilling head, port64 will be sufficiently covered that a large differential pressure willmomentarily exist across plunger 11 to shear the pin 27, thus detonatingsquib 31 to fire the shaped charges. The simplified schematic diagramsof a pair of shaped charges and an interconnecting or syndetic chargeillustrated in FIGS. 4-22 illustrate the manner in which the resultingexplosive jet is formed. The figures show the formation of the explosivejet at one microsecond intervals starting at zero time in FIG. 4. Asillustrated, immediately after ignition of the shaped charge 37, thedetonation front will progress downwardly. At 2 microseconds afterignition the explosive jet begins to form at the apex of the conicalopening of shaped charge 37. The explosive jet increases in size andmaterial content as the shaped charge burns, and gets progressivelylonger even after the shaped charge is completely destroyed. Between 7microseconds and 12 microseconds after ignition of shaped charge 37,only the syndetic charge is burning so that no explosive material willbe added to the explosive jet. At 12 microseconds, the upper end ofshaped charge 49a is ignited and thereafter the explosive jet willcontinue to increase in material content as well as in length andvolume. As illustrated in FIG. 22, at 18 microseconds after ignition ofcharge 49a, the combustion of shaped charge 49a is completed, and theexplosive jet proceeds downwardly through the openings of subsequentshaped charges.

An advantage of the present invention is that the critical standoffdistance for each of the shaped charges is well within the range of l to12 inches required for most effective hole production from shapedcharges. The reason for this is that the hole in the earth issuificiently extended by the jets of previously ignited shaped chargesto provide the optimum standoff distance for a given shaped charge inthe apparatus. Using the apparatus of the present invention, it has beenfound possible to optimize the standoff distance without increasing thecone angle of the shaped charges beyond the optimum. As noted, all ofthe cone angles of the shaped charges are substantially the same.

The above description and examples of the invention are for the purposeof illustration, and it is not intended that the invention be limitedexcept by the scope of the appended claims.

What is claimed is:

1. An explosive assembly for well drilling operations comprising:

an elongated housing terminating in an ogive at one end thereof;

a first shaped explosive charge supported in the other end of saidhousing, having a conical opening facing toward said ogive, the axis ofsaid conical opening being directed substantially at the point of saidogive;

at least one additional shaped explosive charge supported in saidhousing between said first shaped charge and said ogive, each said atleast one additional shaped charge having an opening therethrough, atleast a portion of which is frusto-conical, the axis of saidfrusto-conical portion being substantially colinear with the axis of theconical opening of said one shaped charge;

a syndetic explosive charge interconnecting each adjacent pair of saidshaped charges, the burning time of said syndetic charge being at leastequal to the time required for substantially the entirety of theexplosive jet produced by one of said each adjacent pair of shapedcharges to pass into the opening through the other of said each adjacentpair of shaped charges;

the cone angle of the conical and frusto-conical openings of said shapedcharges being substantially equal; and

differential pressure responsive firing means for igniting said firstshaped charge responsive to hydrostatic pressure of a given magnitude,said differential pressure responsive firing means comprising a sealedhousing section, an igniter charge connected to said first shapedcharge, a firing pin supported in firing position relative to saidigniter charge by means including shear pin means, a cylindrical pistonhousing, a piston in said piston housing having one face exposed tofluid pressure around said sealed housing and an opposed face exposed tofluid pressure in said sealed housing, and compression spring meansdisposed between said piston and said firing pin.

2. The apparatus of claim 1 wherein the burning velocity of saidsyndetic charge is determined by the formula:

where V is the detonation velocity of the syndetic charge,

V is the velocity of the jet formed by the shaped charge, X is theperpendicular distance from the lower end of the shaped chargedetonating the syndetic charge to the upper end of the next lower shapedcharge, and D is the shortest distance from the lower end of the shapedcharge detonating the syndetic charge to the upper end of the next lowershaped charge measured along the syndetic charge.

References Cited by the Examiner UNITED STATES PATENTS 1,474,548 11/43Pape 10 27 2,543,823 3/51 Barry. 2,984,307 5/61 Barnes 10224 FOREIGNPATENTS 10 155,408 2/54 Australia.

999,974 10/51 France. 645,611 11/50 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner. 15 SAMUEL FEINBERG, Examiner.

1. AN EXPLOSIVE ASSEMBLY FOR WELL DRILLING OPERATIONS COMPRISING: ANELONGATED HOUSING TERMINATING IN AN OGIVE AT ONE END THEREOF; A FIRSTSHAPED EXPLOSIVE CHARGE SUPPORTED IN THE OTHER END OF SAID HOUSING,HAVING A CONICAL OPENING FACING TOWARD SAID OGIVE, THE AXIS OF SAIDCONICAL OPENING BEING DIRECTED SUBSTANTIALLY AT THE POINT OF SAID OGIVE;AT LEAST ONE ADDITIONAL SHAPED EXPLOSIVE CHARGE SUPPORTED IN SAIDHOUSING BETWEEN SAID FIRST SHAPED CHARGE AND SAID OGIVE, EACH SAID ATLEAST ONE ADDITIONAL SHAPED CHARGE HAVING AN OPENING THERETHROUGH, ATLEAST A PORTION OF WHICH IS FRUSTO-CONICAL, THE AXIS OF SAIDFRUSTO-CONICAL PORTION BEING SUBSTANTIALLY COLINEAR WITH THE AXIS OF THECONICAL OPENING OF SAID ONE SHAPED CHARGE; A SYNDETIC EXPLOSIVE CHARGEINTERCONNECTING EACH ADJACENT PAIR OF SAID SHAPED CHARGES, THE BURNINGTIME OF SAID SYNDETIC CHARGE BEING AT LEAST EQUAL TO THE TIME REQUIREDFOR SUBSTANTIALLY THE ENTIRETY OF THE EXPLOSIVE JET PRODUCED BY ONE OFSAID EACH ADJACENT PAIR OF SHAPED CHARGES TO PASS INTO THE OPENINGTHROUGH THE OTHER OF SAID EACH ADJACENT PAIR OF SHAPED CHARGES; THE CONEANGLE OF THE CONICAL AND FRUSTO-CONICAL OPENINGS OF SAID SHAPED CHARGESBEING SUBSTANTIALLY EQUAL; ANF